In legal terms "dumping" is only applicable to imports. There's generally nothing illegal about delivering a local service at a loss, except in limited cases when one company has an effective monopoly and uses that pricing to drive out competitors. For now the food delivery market is still highly competitive.

I don't think existing competition law or theory applies to this new phenomenon. The delivery companies are essentially selling at a loss to obtain an overwhelming network effect to become a long term monopoly.

in this case, Uber eats is importing foreign capital and "dumping" it into the system as subsidies to the consumer which are designed to establish a monopoly. They will either fail to establish a monopoly and close shop, or succeed and jack up prices. Whatever term you want to apply here, this doesn't seem like a business practice that should be permitted.